Indirect exhaust system



Feb. 12, 1929.

H. A. ROSELUND INDIRECT EXHAUST SYSTEM ,JlL QA 1927 :lllllllll'lllill4 Patented Feb. 12, 1929.

hairs stares rarsur OFFICE.

HAROLD A. RGSELUND, 0F TOLEDG, OHIO, ASESIGNOB TO THE DE VILBISS COMPANY, OF

TGLEDU, Q'Hl'O, A CORPORATION OF OHIO.

INDIRECT EXHAUST SYSaTEM.

Application filed June 3,

This invention relates to an indirect ex haust system for controlling air circulation, and in its presentembodiment is particularly adapted for use in the art of spray-paint 1 to carry off the fumes or particles of. spray which might otherwise prove deleterious to the health of persons employed in the building where such painting is done.

The successful operation of a system of this nature depends. upon the creation of an outwardly directed draft through a rather large conduit by the inductive action of a stream of air which is forced under considerable pressure into and through said conduit in an outward direction. In thesystems heretofore generally used the stream of air is injected into the large conduit through a smaller conduit the outlet of which is constricted and is centrally disposed within the large conduit. Usually the large conduit is also constricted to a smaller diameter at a point approximately opposite the outlet of the smaller conduit. The current which is induced to flow outwardly by the draft thus created is laden with particles of paint, and in the systems heretofore generally used, some of these particles adhere to the inside of the large conduit and theoutside of the smaller conduit, forming layer upon layer, which gradually fills up the conduit and obstructs the operation of the system. This deposit of paint particles when certain materials are used creates a serious fire hazard and must be frequently removed- Since the constricted or partially obstructed portion of the conduit is disposed at some considerable distance from the spray booth where the spray painting is carried on and is difficult to reach, this necessary cleaning becomes an expensive operation. lhe object of the present invention is to, provide improved means for inducing the desired flow through the conduit, to provide a straight comparatively short exhaust conduit of large diameter uncoustricted and without obstruction of any kind, at the same time establishing an envelope of clean airv around the fume laden current so as to keep the wall of the conduit comparatively clean. These results are obtained with a considerable increase in efficiency, since the static pressure of the in iected blast of air need be only approximately half that required in systems heretofore used 1927. Serial No. 196,386.

to produce the same volume of air flow through the exhaust conduit.

The specific construction and arrangement of the system according to one embodiment of the invention will be fully explained in connection with the accompanying drawing, in which Figure 1 represents a cross section taken through a booth with the invention connected to the rear wall thereof.

Fig. 2 is a section taken on the line 22 of Fig. l. r

Fig. 3 is an enlarged detail view illustrating one way of connecting the conduit to the nozzle leading from the booth.

The invention is shown in connection with a booth 5 within which the painting is done. The rear wall 6 of this booth is preferably spaced far enough from the outer wall 7 of the building to provide a suitable space for installing the exhaust system In the form illustrated in the drawing, a motor 8 is mounted on a base 9 in the rear of the booth and drives a shaft 10 which extends into. a blower casing 11 supported in any suitable manner, as for example by bracket 12 secured to the base 9.

A nozzle 13 of rather large diameter leads rearwardly from the rear side of the booth 5 and. may be secured to the wall 6 by means of a flange 1 and bolts 15. This nozzle 13 is surrounded by a jacket 16 which is connected with the outlet 17 leading from the blower 11. i The rearportion of the jacket 16 tapers rearwardly as indicated at 18 and merges into i a conduit 19 which extends through a window 20 in the outside wall 7 and discharges into the atmosphere outside of the building. The blower 11 is also provided with an air inlet conduit2l which preferably extends to the outside of the building.

The outside diameter of the nozzle 13 is slightly less than the inside diameter of the conduit 19 and it is important that the outlet end of the nozzle Should be securely held in concentric, relation to the inlet end of the conduit. This connection maybe effected by a number of bolts 22v provided with spacing sleeves 28 of the proper length to be inserted between the nozzle and the wall ofthc condu'it.

In exhaust systems as heretofore generally used to carry away'the fumes; resulting from lid spraying, considerable loss of eiliciency has resulted from the accumulation of paint upon the wall of the conduit. in the operation of the present system, clean air from the blower is forced into the jacket 16 and thence into the conduit 19 in a comparatively thin annular sheet which is formed by its passage between the nozzle and the inlet end of the conduit 19. As the air from the blower is' thus forced through the conduit at a considerable velocity, it travels along the surface of the conduit and by its action causes a reduction of pressure in the central portion of the conduit and in the nozzle 13. This induces a flow rearwardly from the booth and thus the operator is fully protected from inhaling any of the poisonous particles. The discharge of the air in this manner along the surface of the conduit tends to preventparticles of spray from adhering to the wall, and requires only approximately half the static aressure required in systems heretofore used, in order to produce the same volume of air flow,

While the system has been devised with .pecial reference to its use in the art of paint spraying, it may also he used advantageously in other relations wherever it is desirable to create a draft to carry away noxious fumes. Its use is of special advantage in removing acid fumes since it makes it unnecessary to use special acid proof fan blades such as are used in direct draft. lVhen used for creating a forced draft for boilers and the like, the result is an improvement over the draft under the grate and requires less power. It may be use; generally to advantage whereever a draft is necessary, and where for any reason it is undesirable to place a fan directly in the conduit or flue. It will be understood that the form of the invention herein shown is merely for the purpose of illustration and that various modifications may be devised in the structure and relation of the various parts of the system without any material change in the results and without departing from the scope of the invention claimed.

hat I claim is:

l. The combination with a booth having an outlet nozzle leading from one of its walls, f an outlet conduit. iuto which said nozzle leads. a chet around said nozzle in spaced relation thereto and connected to the in et end of said conduit, and a blower connected with said jacket, the inlet end of said conduit being concentric with said nozzle and having an internal diameter slightly greater than the external diameter or" the nozzle, providing concentric cylindrical surfaces between which a thin annulansheetof air is discharged under pressure and directed along the interior surface of said conduit.

2. The combination with a booth having an outlet nozzle leading from one of its walls, of an outlet conduit into which said nozzle leads, a jacket around said nozzle in spaced relation thereto, a blower having an outlet leading into said jacket, said jacket having a tapered outlet end joined to the inlet end of said conduit, and means at the juncture of said tapered outlet with the conduit for securing the latter to the outlet end of the nozzle in concentric relation thereto, the internal diameter of said conduit being slightly greater than the external diameter of the nozzle, and providing therewith concentric cylindrical surfaces between which a thin annular sheet of air is discharged under pressure and directed along the interior surface of said conduit.

3. The combination with a conduit, of a nozzle leading into the inlet end of said conduit, the discharge end. of said nozzle being concentric with the conduit and spaced from the wall, thereof, providing in connection therewith concentric cylindrical surfaces, and means for forcing a stream of air between said cylindrical surfaces and through the conduit adjacent the wall thereof to induce a flow through the nozzle and central part of the conduit and tending to prevent the induced flow from coming in contact with the wallet said conduit.

l. The combination with a conduit, of a nozzle leading into the inlet end of said conduit, the discharge end of said nozzle being concentric with the conduitand spaced from the wall thereof, providing in connection therewith concentric cylindrical surfaces, and means for forcing air between said cylindrical surfaces and along the wall of the conduit, to cause a reduction of pressure in the central part of the conduit and in the nozzle, thereby inducing a flow through the nozzle and conduit and tending to prevent the induced flow from coming in contact with the wall of said conduit.

5. The combination with a booth, of a discharge nozzle leading therefrom, a conduit into which said nozzle leads, the outlet portion of the nozzle for a substantial distance from its end being of uniform cross section, with its outer surface at a uniform distance from the inner surface of the conduit, the latter continuing thence with a subr'itantially uniform cross section to its discharge end,

and means for forcing air under pre true etween the nozzle and the wall of the conduit to induce a flow from the booth thrmigh the central part of the conduit and at the same time to keep said induced flow out of contact with the wall of the conduit.

6. The combination with a cylindrical nozzle, of a cylindrical conduit having an inlet end portion within which the discharge end of the nozzle projects for a substantial distance, the inner surface of the conduit being coaxial with and of greater diameter than the outside surface of the nozzle, thus defining an annular passage Way of uniform cross sectional dimensions, and means for forcing air under pressure through said passage way, to be thereby directed in a thin sheet along 5 the inner surface of the conduit, so as to cause an induced flow through the central part of the conduit and tending to prevent any suspended solid particles Which may be carried by said induced flow from adhering to the Wall of said conduit.

In testimony whereof I have hereunto signed my name to this specification.

HAROLD A. ROSELUND. 

